The present invention relates to static control devices in media handling systems, such as printers and copiers; and, more specifically, to static control devices utilizing fine fiber bundles and non-contact ionization for static charge dissipation.
In a commonly used process for electrophotographic printing applications, such as for printers and copiers, a uniform charge is applied to a photoconductive surface on a drum or belt. A light beam, such as from a laser, is used to expose the surface, leaving an electrostatic latent image corresponding to the image to be printed. The latent image is developed by the application of toner particles that adhere to the electrostatic latent image. The toner image is transferred to the media intended to receive the printed image, and is fixed thereon through the application of heat and/or pressure in a fuser.
In a sheet handling device such as a printer or copier, and other machines having sheet handling pathways, electrical charges can build up in media, such as paper, that is transported through the machine. The media transported through such a device, both before and after reception thereon of the toner image, is frictionally contacted by numerous rotating members, and is slid along, over and against various stationary guide members. Consequently, the media can accumulate both positive and negative electric charges, both as a result of transport through the machine and from transfer of chargers from the photoconductive process. Paper will typically accept and hold such charges readily.
Buildup of charges on the media can impact machine performance and function detrimentally. Charges on the media can cause the media to be attracted to or repelled from transport surfaces, interfering with proper transport and indexing of the media for proper printing. Charges in the media also can interfere with transfer of the toner image to the media surface, by attracting stray toner particles thereto, in areas of the sheet not intended to receive a toner image. Such charges also can cause sheets to adhere to each other, causing media jams in the machine.
Thus, it is desirable to remove the electrostatic charges from the sheet. Early attempts at controlling static charges included devices to ionize air surrounding the sheet, thereby providing a pathway to ground. It was also known to contact the sheet directly with conductive strips, providing a more physically continuous grounding path for charges on the sheet. Early ionizing devices were expensive and produced ozone, and contacting devices sliding over a newly formed image as the sheet is transported through the machine degraded the image quality. Thus, neither of these attempts was completely satisfactory.
It also is known to contact the sheet with conductive brushes having fibers secured in a matrix. For example, it is known from U.S. Pat. No. 5,354,607 xe2x80x9cFIBRILLATED PULTRUDED ELECTRONIC COMPONENT STATIC ELIMINATOR DEVICESxe2x80x9d to form pultrusions from densely packed bundles of fibers. One end of the bundle is fibrillated, and the exposed ends thereof contact a surface to be discharged. Other types of both contacting and non-contacting brush-like static charge eliminators are also known.
In another known, brush-like static eliminator, a thin tape of aluminum foil is provided transverse to the paper path in a machine. A plurality of discrete bundles of individual electrically conductive fibers are adhered to the aluminum foil, and can contact or come in close proximity to the surface of a sheet transported along the path. A problem with this design is that aluminum foil can tear easily, and is difficult to apply on a machine in a straight line, which is necessary to maintain constant space from a sheet along the length of the device. It is also known to use an aluminum strip rather than foil. However, the aluminum strip has physical memory, and will tend to curve at the ends thereof, if the aluminum strip was ever provided or stored in a roll. Also, aluminum is subject to oxidation, which reduces the conductivity and increases the surface resistance. If oxidation is significant, the effectiveness of the static control device can be diminished.
Attempts at improving such devices have not met with total success. Using a non-conductor, such as polyester, in the support or carrier strip may eliminate memory problems, but requires incorporation of conductive structures for connecting the fiber bundles to a grounding source. A single fiber or a plurality of fibers running the length of the strip can be used as the conductive structure, but is subject to failure if the continuity thereof is broken. Providing a metal coating on a non-conductive base material to serve as the conductive structure is also effective electrically, but again scratching can cause discontinuity and failure of the device.
What is needed in the art is a rigidly backed static eliminator that has bulk conductivity and corrosion resistance, and facilitates straight installation of the device in a printer, copier or the like.
In one aspect thereof, the present invention provides a static control device with a carrier strip of non-metallic, electrically conductive material. The strip has a length and first and second lateral edges extending along the length. At least one bundle of electrically conductive filaments is attached to the carrier strip, disposed on the strip transverse to the lateral edges and extending beyond at least one of the lateral edges.
In another aspect thereof, the present invention provides a static control system for a media handling apparatus having frame members and conveying devices providing a media path for transporting sheets of media through the apparatus along the media path. A static control device includes a non-metallic conductive carrier strip. The carrier strip has a length and first and second lateral edges. The carrier strip is attached and electrically connected to the frame. At least one bundle of electrically conductive filaments is attached to the carrier strip, the at least one bundle of filaments being disposed on the strip transverse to the lateral edges, and extending beyond at least one of the lateral edges.
In yet another aspect thereof, the present invention provides a static control system for a media handling apparatus with at least one frame member and conveying devices providing a media path for transporting sheets of media through the apparatus along the media path. A static control device includes a flexible, conductive plastic carrier strip, the carrier strip having a length and first and second lateral edges. The carrier strip is attached and electrically connected to the frame, and disposed transverse to media transported along the media path. A plurality of bundles of electrically conductive filaments are attached to the carrier strip, and disposed on the strip transverse to the lateral edges. The filaments have ends disposed in spaced relation to media transported along the media path.
An advantage of the present invention is providing a static control device that is easy to install properly, and that is resistant to corrosion, staining and physical deterioration from contact with common cleaning materials.
Another advantage of the present invention is providing a static control device that is robust, and can withstand a degree of physical damage without compromising its operational effectiveness.
Yet another advantage of the present invention is to provide a static control device that is light weight to reduce shipping expense, has low physical memory to remain flat when installed even if it was previously stored in a roll, and that has smooth edges for increased safety in handling.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features.